Methods of ATM InternetworkingMethods of ATM Internetworking

What is LAN Emulation?What is LAN Emulation?

Lan Emulation provides for:– all existing LAN applications to run over ATM– the use of ATM as a backbone to interconnect existing

“legacy” LANs– the interconnection of ATM-attached

servers/workstations to each other and to those on “legacy” LANs

– multiple Emulated LANs which are logically separate, to use the same physical ATM network

ATMNetwork

EthernetToken Ring

EthernetToken Ring

Physical and Emulated LANsPhysical and Emulated LANs

Scenario 1Scenario 1 An ATM network interconnecting multiple Ethernet

segments and ATM-attached end-systems– Ethernet to Ethernet– Ethernet to ATM– ATM to ATM

EthernetEthernet

ATM-attachedstations

ATMNetwork

Bridge Bridge

Scenario 2Scenario 2 An ATM network interconnecting multiple Token-Ring

rings and ATM-attached end-systems– Token Ring to Token Ring– Token Ring to ATM– ATM to ATM

ATMNetwork

ATM-attachedstations

RingRing

Bridge Bridge

LAN Emulation Protocol StackLAN Emulation Protocol StackATM Host ATM Switch ATM-LAN Bridge LAN Host

NDIS/ODI Driver I/f

ExistingApplications

NDIS/ODI Driver I/f

ExistingApplications

IP

ExistingApplications

IP

AAL5

ATMPhysical Layer

LAN EmulationLAN Emulation

Physical Layer

MAC

ATMPhysical Physical

ATMPhysical

AAL5 MAC

LAN Emulation

LAN Emulation

Bridging

Physical

AAL5

Emulated LAN TypesEmulated LAN Types

An Emulated LAN provides the functionality of a single LAN segment:

– an Ethernet/802.3 segment, or– a Token-Ring/802.5 ring

An Emulated LAN does not emulate all the segment-specific details of the emulated type, e.g.:

– No collisions– No tokens, no beacon frames

LANE ArchitectureLANE Architecture

LAN Emulation Client:ATM Workstation

LAN Emulation UNI

LAN Emulation Client:ATM Bridge

LAN Emulation UNI

LegacyLAN

LAN Emulation Service

InitializationAddress RegistrationAddress ResolutionData Forwarding

LAN Emulation Service

InitializationAddress RegistrationAddress ResolutionData Forwarding

ATM workstation: One LANE Client for each emulated LAN

LE Service ComponentsLE Service Components

LE Configuration Server– Provides configuration information, address of

LE Server LE Server

– Implements Address Registration/ Resolution functions

Broadcast/Unknown Server– Performs all broadcasting and multicasting

and unknown unicast distribution

LE Service ComponentsLE Service Components

LANE Control ConnectionsLANE Control Connections

LAN Emulation Client

Configure Direct V

CC

Control Direct VCC

LE Configuration Server

LE Server

Broadcast/Unknown Server (BUS)

Other LE Clients

Control DistributeVCC

LAN Emulation Client

Multicast Send VCC

Multicast Forward VCC

LE Configuration Server

LE Server

Broadcast/Unknown Server (BUS)

OtherLE Clients

Data Direct VCCs

LANE Data ConnectionsLANE Data Connections

LUNI Protocol OverviewLUNI Protocol Overview Initialization Configuration Joining Registration and BUS

Initialization Data Movement

InitializationInitialization

Must determine the ATM address of the LECS Use SNMP ILMI to get address from a table in the

switch and place call to that address Use well-known ATM address If that fails, use the VPI/VCI 0/17 PVC as the

connection to the LECS If LECS is not available, try the LES

ConfigurationConfiguration

LE Client provides the LECS with:– ATM address– MAC address– LAN types and frame sizes requested

LECS Returns: – LES address– LAN type and frame size to use

JoiningJoining

Create Control Direct bi-directional VCC Transmit Join Request (ATM address, LAN info,

proxy indication, optional MAC address) Possibly accept Control Distribute VCC before Join

Response is received May time out or fail

Registration and BUS InitializationRegistration and BUS Initialization

Register any MAC addresses Resolve 0xffffffffffff MAC address to get ATM

address of BUS Create bi-directional Multicast Send VCC to BUS Accept bi-directional Multicast Forward VCC from

BUS

Data MovementData Movement

When a data frame is available for transmission, check internal cache

If unknown, ask the LES While waiting for response, may transmit

frame(s) via BUS Establish direct connection when response is

received Connections are timed out on inactivity

LAN ApplicationsLAN Applications

The advantage of LAN Emulation is that – the use of ATM is hidden from the applications

The disadvantage of LAN Emulation is (also) that– the use of ATM is hidden from the applications

All existing applications can use LAN-Emulation New applications, in order to use the power to ATM:

– need to be cognizant of ATM, and thus– need to use an ATM-aware API (e.g., Classical IP)

Both types of applications can co-exist, side by side

InteroperabilityInteroperability A logical “subnet” is either an Emulated LAN or an

ATM-aware subnet Logical subnets are interconnected via routers The driver for the ATM-adapter card needs to support

the relevant type of logical subnet.

“ATM-aware”subnet

“ATM-aware”subnet

EmulatedLAN

EmulatedLAN

Router or ATM Server

LAN Emulation Version 2.0LAN Emulation Version 2.0

LUNI 2.0– Compatible with LUNI 1.0– Optional to multiplex ELANs on same VCC– Improved QoS support– Additional support for Multicast– Persistent Data Direct VCCs stay up across server

failures LNNI 2.0

– Multivendor LE service component interoperability– Up to 20 LES/BUS pairs; up to 2000 LE Clients– Standardized server failover– Selective Multicast Server to offload multicasts from

BUS

SummarySummary

All existing LAN applications can run on an Emulated LAN

LAN Emulation allows ATM to be used as a backbone to interconnect “legacy” LANs and ATM-attached hosts

To exploit the power of ATM, new applications need to use ATM-specific API’s, rather than LAN-Emulation